Pivotal role for glycogen synthase kinase–3 in hematopoietic stem cell homeostasis in mice
Jian Huang, Yi Zhang, Alexey Bersenev, W. Timothy O’Brien, Wei Tong, Stephen G. Emerson, Peter S. Klein
Jian Huang, Yi Zhang, Alexey Bersenev, W. Timothy O’Brien, Wei Tong, Stephen G. Emerson, Peter S. Klein
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Research Article Hematology

Pivotal role for glycogen synthase kinase–3 in hematopoietic stem cell homeostasis in mice

Abstract

Hematopoietic stem cell (HSC) homeostasis depends on the balance between self renewal and lineage commitment, but what regulates this decision is not well understood. Using loss-of-function approaches in mice, we found that glycogen synthase kinase–3 (Gsk3) plays a pivotal role in controlling the decision between self renewal and differentiation of HSCs. Disruption of Gsk3 in BM transiently expanded phenotypic HSCs in a β-catenin–dependent manner, consistent with a role for Wnt signaling in HSC homeostasis. However, in assays of long-term HSC function, disruption of Gsk3 progressively depleted HSCs through activation of mammalian target of rapamycin (mTOR). This long-term HSC depletion was prevented by mTOR inhibition and exacerbated by β-catenin knockout. Thus, GSK-3 regulated both Wnt and mTOR signaling in mouse HSCs, with these pathways promoting HSC self renewal and lineage commitment, respectively, such that inhibition of Gsk3 in the presence of rapamycin expanded the HSC pool in vivo. These findings identify unexpected functions for GSK-3 in mouse HSC homeostasis, suggest a therapeutic approach to expand HSCs in vivo using currently available medications that target GSK-3 and mTOR, and provide a compelling explanation for the clinically prevalent hematopoietic effects observed in individuals prescribed the GSK-3 inhibitor lithium.

Authors

Jian Huang, Yi Zhang, Alexey Bersenev, W. Timothy O’Brien, Wei Tong, Stephen G. Emerson, Peter S. Klein

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Figure 2

Gsk3 knockdown increases cycling of the HSC-enriched LSK cell population.

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Gsk3 knockdown increases cycling of the HSC-enriched LSK cell populatio...
(A) To assess cell cycle status of the HSC-enriched LSK population, sorted GFP+ LSK and GFP+ LSK Flk2– cells from primary recipients of control and Gsk3-rnai 4 months after BM transplantation were stained with Hoechst and Pyronin and analyzed by FCM. Representative FACS data are shown for control versus Gsk3-rnai-C2. (B) At 4 months after BM transplantation, primary recipients of control and Gsk3-rnai were fed BrdU in the drinking water for 7 days. Sorted GFP+ LSK Flk2+ and Flk2– cells were stained with BrdU-APC antibody and PI to analyze BrdU incorporation. Representative FACS data are shown for control versus Gsk3-rnai-C2. Similar results were obtained by BrdU versus 7-AAD staining (BD). Percent cells are shown for the indicated gates and quadrants. In A and B, lower left gate represents G0, upper left represents G1, and upper right represents S, G2, and M phases of the cell cycle, as shown in the diagram in A.